The objectives of this project are (a) to extablish the morphologic basis for glomerular permeability in the normal kidney, examining particularly the relative importance of the glomerular basement membrane and the epithelial slit diaphragm as barriers to the passage of macromolecules; and (b) to determine the mechanisms of proteinuria in several kinds of experimental renal disease, including aminonucleoside nephrosis, nephrotoxic (anti-glomerular basement membrane) nephritis, and Heemann's (autologous immune complex) nephritis.